change the global variable value from function in bge?
This is, no kidding, straight from my professors mouth.

There are three scopes of Variables; one does not apply to blender.


Local
Form-Level
Global


Local variables would be like game properties, or a material.
They have effect on only those procedures and functions who posses them and objects/procedures designed to be affected by them via collision, near, ray, radar ect.

They can only be changed/accessed via the procedures/functions to which they belong.

Global variables (this is the real answer) can be changed, accessed, and modified by any/all procedures, functions, and objects.

This means Yes. If it is on one, it's on 'em all.